The present invention generally relates to integrating the controls for engine start/stop operations with the controls for exhaust gas after-treatment systems. More particularly, embodiments of the present invention relate to controlling engine start/stop operations based at least in part on the thermal management of an exhaust gas after-treatment system.
Start/stop controls are often configured to utilize opportunities to stop an engine of a vehicle so as to at least attempt to reduce fuel consumption, and thus reduce fuel costs, while also mitigating emissions. Existing start/stop controls often use certain engine conditions, such as, for example, engine coolant temperature, ambient conditions, and engine battery levels to limit start/stop operations for the purpose of engine protection and operator comfort.
Selective catalytic reduction systems (SCR) typically are configured to provide one or more catalyst elements that, with the aid of a reductant, convert nitrogen oxides (NOx) in exhaust gases into nitrogen (N2) and water. The efficiency of chemical reactions by an SCR catalyst may depend on a variety of different factors, including, for example, at least on the properties of the exhaust gas, such as, for example, an inlet temperature and/or velocity of the exhaust gas steam that enters into the SCR. Further, such properties of the exhaust gas stream, and moreover the efficiency of the after-treatment system, may change based on a variety of different factors, such as, for example, operating conditions, including, but not limited to, ambient conditions, engine load, duration of periods of engine idling, and engine temperatures when an engine is stopped and/or re-started by a start/stop operation, among other factors. As a consequence, under such operating conditions, the emissions released from the after-treatment system may, at times, exceed a target, or regulation specified, amount.
In many leading exhaust gas emission markets, emission transparency is a requirement for obtaining dedication certification. Yet, existing start/stop control strategies generally do not take into account the impact start/stop operations may have on the thermal management of the after-treatment system, and moreover the impact start/stop operations may have on exhaust gas emissions. For example, existing start/stop control strategies typically do not take into account modern SCR controls and systems. Further, by not taking into account at least SCR controls and systems, existing start/stop controls may be unable to demonstrate emission transparency as, again, is required by at least some exhaust gas emission markets.